Small cargo ship

[chrisdn]

Mt god in heaven...a fuscia spaceship!!! He he, is it called the blue oyster or what? He He

You should build some clamps/mounts onto the exo skeleton fo cargo containers or weapons if needed. Imagine the surface bristling with missiles or cannons...would look pretty good.

Reworked the engine nozzles and mount for Atlantia. I'm pretty happy with but I have no doubt there will be something I've missed.

Speak to you soon bud.

[chuck_starchaser]

It's not the ship's color; I'd just placed a strong purple light.
Yeah, I've been thinking of putting missile launchers, like rotating boxes, at the X-crossings. Or at least mounts. Thing is, to represent mounts I can do it in the texture: Black dot in the middle, four smaller black dots in towards the corners, of the little squares.
Those engines are looking great. Just scale up the circle at the front of the forward section; it's too small.

Exoskel is not finished yet but almost...



Just need to cut off the round part protruding forward of the front plate and add some kind of hinge for the forward micrometeorite shield that's to come, as well as brackets for the attitude thruster clusters.
Needless to say, the cones on the side plates are where the lateral, add-on containers insert. There will be small, square holes for latches and stuff, but I can represent those by painting them black in the texture. The set of smller cones near the middle are where tug ships attach. Once you get pretty close to your destination, tug ships come to get you and take you to the docking spot. When you're leaving, they give you a push in the general direction you're going, as you're not allowed to turn your engines on while too close to a station. People who live and work at stations don't appreciate high energy plasma splashes.

[dandandaman]

The micrometeorite shield is a tricky one...since you'll be facing both ways I guess with large velocities relative to the orbital plane. So you'll need engine protection too somehow?

Either way, now that you just mentioned it i thought I might make the suggestion of having the docking ports on the side, and having the cargo bay/tank thing covered in a shield rather than having one seperate. ie the shield is built onto the hull. That way you just need to worry about an aft mechanism for engine protection...

[chuck_starchaser]

Indeed, I'll have another pivoting shield on the back. Unfortunetely it won't be able to cover the exhaust; but I'm hoping against hope that the smaller particles would be blown away by the exhaust itself. Crossing fingers and toes...

That's a good idea, but I think I got the problem well taken care of. Of course, I haven't shown any of the detachable cargo hulls, but they'll come with shields built onto them, at both forward and aft ends.

The riskiest part in a trip will be in the middle, when the ship has to turn around. On a trip to Pluto, you'd be going at 1800 km per second at that point. That's why I chose the sides over the front, for extra cargo; I was more worried about moment of inertia than about extra shielding.
I've been thinking of maximizing the rotational speed by having powerful solid fuel thrusters you replace each time you dock. Cheap, powerful, single use, non-throttable. You'd have four of them. Two of them would burn out first to give the ship a nice angular speed to get started. At the end of the maneuver, the other two burn out to help stop your rotation. And then the liquid fuel thrusters can make adjustments.

[Zeog]

Alternatively, you could leave the shields away and let instead welding bots roam the surface of your ship. That would certainly look much cooler. Micro meteorites don't make big holes. So, one could fix them before depressurization happens. I have some parts of such a six-legged robot as a blender file at home. Interested?
Apart from that, if you really need a shield because the hull of you ship is too thin to stop them, then your shield has to be very thick, which means a lot of additional mass. I'm not sure if you really want that, since a greater mass could spoil your acceleration efficiency. On the other hand, if you say that your shield is some "special material" capable to stop little fast flying objects with only little mass, then why not make the hull out of it?

There is another thought, ever thought of aerogel for stopping micro meteorites? Covering the hull with something like that could be your solution!

[chuck_starchaser]

I'd be mighty interested in that robot!

Yeah, I saw some article somewhere about some self-healing material.
Anyhow, I'm no physicist but, my mental model about shielding, currently, is that by putting a sheet of metal some distance forward, although relatively thin, we'd cause the particles to break up into smaller ones. I wasn't thinking of the shield "stopping" the particles, necessarily, but rather a particle of sufficient size (tenth of a millimeter) would vaporize a hole out of the sheet metal, but by the same token lose a lot of energy and split into a spray of sub-particles.
Then again, perhaps a ceramic would be better in that it would take much higher temperature to vaporize.
BTW, it's not that the hull is that thin, but rather that the shield is easily replaceable and cheap.
Not sure aerogel would work, unless it was very thick. Maybe for collecting samples
It's not so worrisome; like there aren't *that* many particles to worry about, but at the speeds we can reach, after accelerating continuously at 0.3 G for a week or two... I mean, normal micrometeorites might hit you at what? 10km/sec? 30km/sec? But when we're moving at 1800km/sec, better watch out. I think anything bigger than a tenth of a millimeter would be fatal, at such speeds.

[chrisdn]

DOn't forget about the new self healing materials under development, in a year or 2 they'll be up to speed and I would suggest you using that material for the ships skin and then use an aerogel type material to absorb impact inertia.

I would have said that the docking ports would have made more sense positioned to the port and starbord with a retractable telescope tube to extend to the stations docking pylons. I would think that in the future they would have standard widths of cargo vessels to allow for easy docking. Ships have certain maximum widths- most notably PANAMAX vessels, who are designed to go through the Panama Canal. In the same way a max width could be applied to freighters in space allowing them to all to fit into a dual docking port (port SBD and Port). Something similar to the berths in Starship Troopers.

Your decel cycle is going to be very hazadous to the amount of pipework you have on the stern, I would suggest putting permamnet shielding around those components or there'll be one big bang.

[chuck_starchaser]

Indeed, like I said, there will be shielding from the back. Not fixed, though; pivoting because it blocks visibility otherwise. Same with the front shield: It will pivot from underneath the ship. Same for the front and rear windows. Some time after you leave port, and before you pick up too much speed, you press a button and the shields come down and cover the windows.

Having the ports in the front has another advantage: maximizes docking space utilization at stations. You can fit more ships this way.

A telescopic docking port would be a technical problem. And I'm not sure there's a problem that it solves. Maintenance workers need access to all sides of the ship no matter which side it docks from; and the loading and unloading of goods must have priority for economic reasons. You want the docking connection to be as short as possible to minimize the time it takes to move cargo in and out. Remember that, once you're docked, you're in zero gravity again. The "forklifts" will be compressed air propelled, and the last thing they need is long tubes to navigate while carrying heavy containers.

[chrisdn]

Don't forget that the 2 main points of weakness on the ship are the cargo hatches and the engine piping etc. Most vessels are loaded form Port or STBD...the only exception are RoRo ships and they carry vehilces.

I wouldn't have thought a forklift would have much trouble navigating a straight telescopic shaft exactly the same diameter as the cargo hatch??? Access crews would also still have access to the entire surface of the ship.

I'll draw a diagram to show you what I mean...think it'll be easier that way.

[chuck_starchaser]

Ships on water need to have containers lifted by crane, then lowered into the hold. That's one reason for having piers. But in a zero gravity situation I'm not sure it makes a difference, whether from the side or front. Also, ocean ships need to be long and narrow, making frontal loading inefficient. Spaceships might need to be long and narrow overall for different reasons, but the cargo container itself doesn't have to be long and narrow, and it is best being all at one place, as opposed to large watercraft that need their cargo weight to be distributed fairly evenly, for structural integrity concerns. So, the way I see it, the traditional pier loses its justifications. I see docking areas as being more like flat walls full of hatches of a few standard sizes and spacings; and telescopic cabins that come out of those walls carrying maintenance crews that work around ships, mostly via manipulators on the fronts of their cabins, and sometimes on EVA (you get charged extra ).

EDIT:
What's the idea about aerogel? Don't get me wrong; I love aerogel; but why would it be better than other materials at stopping particles? I understand its use for a sample return, in that a piece of metal would destroy, rather than capture the particles; but is it also well suited for use as a "shield"?

[chrisdn]

Aerogel will last longer and be easier to apply to the hull through a nozzle to the hull...the idea is that it takes all the momentum out of particle but doesn't explode like steel armour would...It would slowly get eaten away through time and might only need renewing once a year or so.

[chuck_starchaser]

Allright, after a short break, steering thrusters brewing...



Explanations: Each cluster has 2 forward, 1 lateral and 1 vertical thrusters of dual liquid propelland, plus a one-time solid/liquid propellant for the mid-trip, turnaround maneuver. The latter thruster is the bigger one; and the fuel could be laughing gas and tire rubber, like the engine on Rutan's Space Ship One. The structures in the middle will hold the fuel tanks for the liquid propellant thrusters, the valve panels, the helium pusher gas tank, and 2 ion drives used for continuous fine adjustments during a trip.

[Zeog]

Here are the parts of the welding bot, I was talking of. Just parts of it!
First there is one of its six legs. It's equipped with a coil that provides the magnetic field, so that the bot can roam the metall surface of the ship. Six legs are more stable than fewer, don't require that much processing power for walking as for instance two and provide some redundancy just in case the bot is hit in the middle of a battle.


The bot itself is rather bug-shaped with its six legs. It has some heavy shielding so that it can perform its tasks in every situation. The bug's wings are the shield. Under the wings (removed in the first picture) is the central energy unit (blue glowing) and the two pressure tanks (red) than contain the fuels for the welding tasks. These pressure bottles can be easily mounted and unmounted from behind once the wings are up. The spheres are the "actuators" and mount point for the legs.
The front of the bot (yet unmodeled) shall provide the actual welding tools as well as additional sensors. In critical situations the bot enters a protection mode in which it stops all its activities closes even the front shielding and "sucks" itself crouching with its coils onto the ship's surface.

The interior viewed from behind.


The left protection shield is now closing (the right one is omitted due to better visibility.)


PM me if you'd like the blend-file.

[chuck_starchaser]

Looks very, very cool. I'm having an idea for a larger, space station based model, with space for a small crew, whose mandate would be to add visual inspection to the bot's capabilities. Of course, it would move intertially most of the time and only extend its legs to the surface for support during work.
Writing the walking AI might be something. I had an old Game Developer mag with a spider walk algorithm; I'll see if I can dig it up.

EDIT: I'm thinking of another possibility: Instead of a standard walking algorithm, we could implement a very simple inverse kinematics algo: Move the body slowly along, and at each iteration, check for each of the legs whether there is a more comfortable (shorter distance) vertex on the body of the ship that it could rest on, than the one it rests on presently, and if so initiate a leg motion to the new vertex.

[klauss]

That thruster assembly doesn't look like a load-bearing structure. You have to think in which way will forces be transmitted, provide such "force sink paths", and reinforce them.

[chuck_starchaser]

You got it; that's my main struggle. When I started by putting support structures I ran out of space for the thrusters and fuel; so I figured, might as well layout the unit first and then figure how it attaches. But now I'm not sure how it attaches :-/

[Zeog]

I don't want to scrap your concepts, but have you ever considered a massive gyro for turning your ship instead of maneuvering thrusters? It would have to be positioned at best at the center of mass of your ship. Rotate it in one direction and the ship starts rotating into the other. To achieve a usable ship turning rate the gyro needs a big moment of inertia (large radius or mass) or has to spin very fast. On the other hand it would look quite boring compared to your fully greebled thruster module.

[chuck_starchaser]

Yeah, that's possible; I did count on having a gyro, though not a massive one. My thinking has been, so far, of having 5 attitude control systems. Starting from most powerful, roughly:

1) Solid fuel thrusters (one use, for mid-trip turnaround)
2) Liquid fuel thrusters (occasional use)
3) Shifting weights (the engine is almost always thrusting forward, so by unbalancing the weight you get to turn). This is a must have, as cargo weight distribution may not be exact, or may shift in flight.
4) Ion drives
5) Small gyro.

The nav computer would use some combination of the last 3 at all times. Probably each time you breath, in the ship, would result in some tiny compensatory action.

WRT large gyros, I believe they are, or were used, in sea-going ships to reduce wave-caused roll. Probably chrisdn will update us on this. I'm not sure about their being used on aircraft or spacecraft due to weight and, I suppose, maintenace concerns. Well, spacecraft do have gyros a lot of the time, but usually small ones, just to perform corrections too small to justify using fuel. But I'm sure ion drives and microdrives are changing the picture as we speak.
Not sure how big a gyro would have to be to apply a significant turning force in a 300 meter long ship...

[Zeog]

Some numbers for a large gyro:
Assume your gyro is a ball of steel (10m diameter) that rotates with 100 revolutions per second. Assume further, that your ship is a cylinder with its center of mass exactly in the middle (300m long, radius 100m, solid steel also--you ship is probably easier to handle ). The rotational axis of ship and gyro are the same and are assumed to be perpendicular to the ship's long axis. Then after some math... the time for a full 360° ship-turn is 25 hours.
The gyro, however, has a mass of 4110 (metric) tons which you have to carry around all the time... You can optimize its geometry, though, but it's still going to choke you. But as long as you have enough electricity to run it you'll be always able to turn. No runing out of fuel (at least for turning thrusters)

[chuck_starchaser]

Makes intuitive sense. Now, optimizing the gyro for mass... I read an article many years ago, about using gyros for energy storage, and it mentioned that while most commonly flywheels are designed with most of their mass along the perimeter, if one wants to maximize energy storage, spinning the wheel close to the limit of material strength, then the optimal shape has most of the mass near the center and decreasing in thickness exponentially towards the periphery. That's for maximizing energy storage, tho, as opposed to its gyroscopic effect.
Yeah, I would think the mass of a large gyro would be too much. Specially when you consider that this ship already has a means for attitude control that comes for free, fuel-wise: 2-axis moving weights that work by offsetting the center of mass, so as to tap on main engine thrust to produce a turning force.

[chrisdn]

The idea of using a gyro is a good one but the thing would have to have a hell of a mass to offset the ship when it's fully laden. Sea going vessels using them for navigation and not alot more. They do , however have different methods of balancing the ship (ballasting). Cruise ships are no using ultra high speed pumps to pump ballast from different tanks in the vessel to offset pitch and roll. I suppose a similar system could be used to offset the attitude of a space ship. Using something like mercury and pumping it at high speed from Port to STBD or vice versa. The momentum carried by the liquid should push the ship in either direction.
I don't really know what liquid would be best, baically the denser the better.

[chrisdn]

The idea of using a gyro is a good one but the thing would have to have a hell of a mass to offset the ship when it's fully laden. Sea going vessels using them for navigation and not alot more. They do , however have different methods of balancing the ship (ballasting). Cruise ships are no using ultra high speed pumps to pump ballast from different tanks in the vessel to offset pitch and roll. I suppose a similar system could be used to offset the attitude of a space ship. Using something like mercury and pumping it at high speed from Port to STBD or vice versa. The momentum carried by the liquid should push the ship in either direction.
I don't really know what liquid would be best, baically the denser the better.

[klauss]

The momentum carried by the liquid should push the ship in either direction.

No, it wouldn't.
Interaction between elements of a system does not affect the movement of the system as a whole.
It might tilt it, though.

[Zeog]

The momentum carried by the liquid should push the ship in either direction.

No, it wouldn't.
Interaction between elements of a system does not affect the movement of the system as a whole.

Depends on what you mean by "the ship moves". If "the ship moves"=="its center of mass moves", then no. The center of mass stays where it is without an external force. But you are free to arrange all masses internally. So when you transfer your cargo into one direction the ship's hull moves into the other direction. Therefore, if "ship moves"=="its hull moves", then yes.

[klauss]

For course corrections, you need to change the direction in which the ship moves. That would imply a movement of the center of mass. You don't move the center of mass - hence, you don't change your course.

But... if you have a big engine on your back, that now is pointing in a different direction...